1. Field of the Invention
The present invention relates to a method for molding a sand mold, in which sand is packed in a mold and solidified to mold a sand mold for casting, and a sand mold.
2. Description of the Related Art
When casting a cylinder block, a cylinder head, or the like of an engine, a collapsible sand core (sand mold) is used for forming a hollow part such as a water jacket, an intake and exhaust port, or the like. WO 2007/058254 describes a starch-based compound that is an organic substance is used as a binder, the binder is stirred and foamed together with an aggregate, a surfactant, a crosslinking agent and water to form foamed sand, and the foamed sand is solidified to mold a sand core for casting.
According to this, although the starch-based binder generates CO2 and H2O when decomposed by heating with a high temperature melt during casting, it does not generate a harmful gas or an odor. Further, since the starch-based binder becomes collapsible owing to pyrolysis, also core sand can be easily ejected after casting.
However, as was described above, the binder is heated with a high-temperature melt during casting to generate CO2 and H2O; accordingly, in a casting metallic mold, a measure for exhausting these gases has to be applied.